This invention relates to compositions and methods for treating ectoparasite infestations on mammalian bodies, particularly human head lice infestations.
Current methods for the treatment of ectoparasites, e.g. lice, typically utilize insecticidal compositions which are available in both prescription and over-the-counter formulations. Such compositions generally include one or more of the active ingredients benzyl benzoate, pyrethrin, permithrin, and lindane. Dispensing formulations include lotions, creams, shampoos, cream rinses, and gels.
However, increasing numbers of ectoparasite infections, especially head lice, that are resistant to the above insecticides have been reported in the medical literature.
Alternative insecticidal treatments such as the use of malathion, ivermectin, and a combination of trimethoprirn and sulfamethazole have been tried, but usually only with mixed results.
Another approach that has been reported and which is at least partially effective is the use of a topical petrolatum-containing product, which suffocate the parasites when left on the head for a prolonged period of time. However, removal of the petrolatum from the head and hair has proven to be a difficult problem, often taking about ten days for complete removal.
Oil based occlusive treatments have been observed to significantly immobilize and coat the lice long enough for asphyxiation to occur. However, some adult lice survived even after an overnight treatment. Meinking, T L, Burkhart C G, Burkhart C N, Ectoparasitic Disease in Dermatology: Reassessment of Scabies and Pediculosis, Advances in Dermatology, Chapter 3, pp 99, Mosby Inc. 1999.
Head lice have been on the increase in the recent past, in large part due to the fact that they have become more tolerant or resistant to conventional treatments. For this reason children are being over-treated with pesticide-containing products as well as other unconventional treatments in an effort to control this epidemic. Many parents and health professionals have turned to unproven and generally ineffective alternative products such as mayonnaise, olive oil, etc. Unfortunately, others have turned to very dangerous alternatives such as gasoline, kerosene or traumatizing measures such as head shaving.
It was recently discovered by the present inventor that ectoparasites on animal skin can be treated successfully by a method comprising the steps of:
I) applying to the skin affected by ectoparasites a water-soluble or water-dispersible, substantially air-impermeable liquid barrier composition;
II) leaving the composition in contact with the skin until the ectoparasites have been killed by suffocation; and
III) removing the composition and the dead ectoparasites from the skin.
See U.S. Pat. Nos. 5,858,383 and 6,139,859.
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients used herein are to be understood as modified in all instances by the term xe2x80x9caboutxe2x80x9d.
It has now been discovered that water-soluble or water-dispersible, substantially air-impermeable liquid barrier compositions that contain monohydric aralkyl alcohols effectively prevent the ectoparasites from closing their respiratory systems (breathing apparatus), called breathing spiracles in lice.
Ectoparasites such as lice, especially head lice, can normally defend against asphyxiation for prolonged periods of time, even up to 12 hours, by closing their spiracles. With the compositions of the invention asphyxiation occurs in very much shorter periods of time, e.g. in less than 45 minutes, usually between 10 and 15 minutes. This is much faster than expected since occlusion of the lice with other materials and compositions will take at least several hours to result in asphyxiation.
The invention also relates to the use of the compositions of the invention for treating ectoparasites on animal skin and hair by a method comprising the steps of:
I) applying to skin and hair affected by ectoparasites a water-soluble or water-dispersible, substantially air-impermeable, pharmacologically acceptable, liquid barrier composition containing one or more aralkyl alcohols in a quantity sufficient to prevent the ectoparasites from closing their respiratory systems;
II) leaving the composition in contact with the skin and hair until the ectoparasites have been killed by suffocation; and
III) removing the composition and the dead ectoparasites from the skin and hair.
The monohydric aralkyl alcohols used in the compositions and methods of the invention are those in which the hydroxyl group is attached to an alkyl group. The aryl moiety is preferably a phenyl or substituted phenyl group, although other aryl groups such as those with multiple rings are also within the scope of the invention provided the resulting aralkyl alcohol is pharmacologically compatible when applied as a component of compositions of the invention to animal skin and hair.
Preferred monohydric aralkyl alcohols of the invention are those having formula I below: 
In which R is a C1-C12 straight or branched chain, saturated or olefinically unsaturated, alkylene group, and R1 and R2 are independently hydrogen, halogen (fluorine, chlorine, bromine, or iodine), C1-C4 alkyl, or C1-C4 alkoxy groups. Preferred compounds of formula I are those in which the R group is a C1-C6 saturated alkylene group, especially those wherein R1 and R2 are both hydrogen. The most preferred compound of formula I is benzyl alcohol. When the R group is an ethylenically unsaturated alkylene group, this group can also be referred to as an alkenylene group.